The world's largest saltwater crocodile in captivity has died, moving villagers to tears in a backwater southern Philippine town that shot to international prominence and started to draw tourists, revenue and development because of the immense reptile.

A veterinarian rushed to far-flung Bunawan town in Agusan del Sur province to check the 900kg crocodile after it flipped over with a bloated stomach Sunday [Monday NZ time] in its cage in an eco-tourism park. The reptile was declared dead a few hours later, Bunawan town Mayor Edwin Cox Elorde said.

Guinness World Records proclaimed the giant, blamed for deadly attacks before it was captured in 2011, the largest saltwater crocodile in captivity last year, saying it measured 6.17 metres. The reptile took the top spot from an Australian crocodile that measured more than 5 metres and weighed nearly a ton.

Authorities will try to determine what caused the death of the reptile, which had become a star attraction of the marshy town of 37,000 people about 830 km southeast of Manila, Elorde said.

Experts estimate that the crocodile was more than 50 years old, according to Elorde.

Veterinarian Alex Collantes said he and park personnel tried to revive the crocodile by immersing it in lukewarm water amid the unusually cold weather this month that may have affected the reptile's condition. But the crocodile died, sending its caretaker and some villagers that gathered at the park to tears, he said.

"I'm really depressed," Elorde said by telephone from Bunawan. "I've come to love that crocodile. It had brought fame to our town and the Philippines."

The crocodile's capture in September 2011 sparked celebrations in Bunawan, but it also fostered concerns that more giant crocodiles might lurk in a marshland and creek where villagers fish. The crocodile was captured with steel cable traps during a three-week hunt after a child was killed in 2009 and a fisherman went missing. Water buffalos have also been attacked by crocodiles in the area.

About 100 people led by Elorde pulled the crocodile from a creek using a rope and then hoisted it by crane onto a truck. It was named "Lolong" after a government environmental officer who died from a heart attack after traveling to Bunawan to help capture the beast, Elorde said.

Bunawan town officials built an eco-tourism park to house the crocodile, which had started to draw local and foreign tourists and bring revenue to the laid-back community.

Philippine officials were planning to start constructing a 1.9-km road to the park to accommodate the growing number of tourists, but it is unclear if the plan will now push through, Elorde said.

He said he planned to have the crocodile preserved so Bunawan villagers can still marvel at it.

"I'd like them to see the crocodile that broke a world record and put our town on the map," Elorde said.